The inventive concepts described herein relate to a semiconductor memory, and more particularly, relate to a volatile semiconductor memory device and a refresh leveraging driving method thereof.
If at least one memory cell in a semiconductor memory device, such as a dynamic random access memory DRAM), is defective, the semiconductor memory device may not perform a required function normally. In this case, the semiconductor memory device may be discarded. However, discarding semiconductor memory devices due to a few defective memory cells is inefficient in terms of a yield.
A semiconductor memory device may include redundancy memory cells. When the semiconductor memory device includes defective memory cells, the defective memory cells may be replaced with the redundancy memory cells of the semiconductor memory device. In this case, the semiconductor memory device may continue to be used. This may mean that a yield may be improved.
A repair operation of a memory device using redundancy memory cells may be accomplished by replacing defective memory cells with redundancy memory cells by a row/column unit. If defective memory cells are detected at a test level after a wafer is processed, addresses of the defective memory cells may be replaced with addresses of redundancy memory cells. In the case that an address signal corresponding to a defective line is received, it may be provided to a spare line instead of the defective line. A row repair operation may be performed through a repair logic circuit, for example, by a unit of four word lines.
A general refresh leveraging (GRL) scheme for reinforcing the refresh ability may be applied to a semiconductor memory device (e.g., DRAM) to improve a data retention characteristic of a weak memory cell. Memory cells determined to be soft failed at a test level may be not repaired with redundancy memory cells but used as normal memory cells. Soft-failed memory cells, that is, weak memory cells may be specifically managed in comparison with normal memory cells. If the GRL scheme is used, weak memory cells may be refreshed more frequently in comparison with normal memory cells at a refresh mode of operation. In general, a GRL operation may be performed by a word line unit.